Home / system #1228
Riello NXHM
Caernarfon, Gwynedd · Mid-terrace · 50 m² · Pre-1900 · 6 kW · radiators · installed by Menai Heating
Last 7 days
169 hourly rows · MID-class heat meter present: yes
3.50efficiency (COP) over 169 hours, from the heat meter
better than 37% of the metered fleet in January 2026
better than 37% of the metered fleet in January 2026
- Electricity used
- 38 kWh
- Heat delivered
- 133 kWh (heat meter)
- Estimate without heat meter
- flow sensor 1.86 · temperature model 3.95
- Mean outdoor temperature
- 8.0 °C · 66 space-heating hours · cooling 0 kWh removed (0 kWh electricity), kept out of the COP
- Flow temperature at 0 °C outside
- 32.6 °C (curve slope 0.12 per K)
- Flow − return while heating
- 0.9 K
- House needs at −3 °C
- 0.9 kW (unit rated 6 kW) · fit r² 0.08
- Hot water
- 33% of electricity, COP 3.36
warningOnly 0.9 K between flow and return
Circulation pump may be set too high or emitters are undersized for the low flow temperature. Ask the installer to check pump speed.
warningHot water uses 33% of electricity at COP 3.36
Lower the tank target to 45–48 °C, heat water once a day in the warmest hours, and disable weekly legionella cycles unless required.
infoUnit is rated 6 kW but the house needs about 0.9 kW at −3 °C
Oversizing causes cycling in mild weather. Cannot be fixed cheaply now, but the curve and minimum run time can limit the damage.
valueReaching the fleet’s January median (3.69) would have saved about £0 in this window at 0.25 GBP/kWh. An estimate, not a promise.
Day by day
electricity per daydaily COP3.0 floor
The installed heating curve
one heating hourfitted curve50 °C
Public system published by its owner on HeatpumpMonitor.org. Cycling (starts per hour) comes from the site’s 365-day statistic. Findings use installer rules of thumb; see methodology.